There are several known means of connecting circuit terminals which are located on one electronic device to circuit terminals which are located on another electronic device, or to terminals of plated circuits located on substrates, or for attaching connection terminals such as solder leads to circuit terminals such as the plated termination on a crystal blank. The known means include soldering and welding. These means provide a mechanical and electrical bond between the terminals.
Solder is used most prevalently, and is very successfully employed in situations wherein there is sufficient rigidity between the terminals which are metal based and which are electrically and mechanically bonded by the solder itself, as for instance, for small parts soldered to a circuit board. However, there are some instances where such rigidity cannot easily be provided, or in fact, is not desired. One example of such an instance is in the attachment of solder leads to crystal blanks, wherein a compliant attachment is highly desirable to avoid dampening the crystal vibration. There are other instances where soldering to the substrate circuit terminations does not work well. One example of such an instance is the attachment of electronic circuits or conductors (such as flexible circuit conductors) to glass substrates having conductive ceramic surface platings such as Indium-Tin oxide provided thereon, which are unsolderable because solder will not "wet" to the Indium-Tin oxide.
In the two instances mentioned above, crystal lead attachment and glass connections, polymeric conductive adhesives are used with success in some environments. However, problems have been experienced with some electronic devices using available conductive adhesives, such as single component silver filled conductive epoxies. In particular, under temperature and humidity stress, the electrical bonds as well as the mechanical bonds deteriorate, leading to circuit malfunctions. The type of environmental conditions leading to this situation typically exceed the normal office environment, but are typical of the environmental conditions encountered in more rugged applications such as portable paging receivers and portable radio use. Circuit malfunctions of these types are often insidious and usually lead to customer dissatisfaction.
Thus, what is needed is an improved mechanical and electrical bonding material usable for compliant connections and for unsolderable connections.